Title of Invention

ELECTRONICALLY ACTIVE ARTICLE, POWER CABLE INCORPORATING IT AND METHOD FOR ITS PRODUCTION

Abstract The invention discloses an electronically active article (10), comprising: a substrate (12); a first buffer film (14) disposed on said substrate, said first buffer film having uniaxial crystal texture characterized by (i) texture in a first crystallographic direction that extends out-of- plane of the first buffer film with no significant texture in a second direction that extends in- plane of the first buffer film, or (ii) texture in a first crystallographic direction that extends in- plane of the first buffer film with no significant texture in a second direction that extends out- of-plane of the first buffer film; a second buffer film (16) disposed on said first buffer film, said second buffer film having a biaxial crystal texture; and an electronically active layer (18) disposed on said second buffer film, wherein said electronically active layer (18) provides a Jc of at least 0.5 MA/cm2 at 77 K and self-field, if the electronically active layer (18) is a superconductor. The invention is also for producing said article and power cable incorporating it.
Full Text FIELD OF THE INVENTION
[0001] The invention relates to biaxially textured buffer layers and articles, devices
and systems made therefrom, including superconductor wires and tapes.
BACKGROUND OF THE INVENTION
[0002] Much of the effort to develop a high temperature superconducting (HTS) wire
or tape has focused on coated conductors based on the epitaxial growth of high temperature
superconducting (HTS) films on tapes that possess a biaxially-textured surface.
Superconducting films with critical current densities in excess of 1 MA/cm2 at 77 K and self-
Field have been achieved for epitaxial TBa2Cu3O7 films on biaxially-textured tapes
produced either by ion-beam assisted deposition (IB AD) or thermomechanically-textured
metals.
[0003] In previous work involving IB AD, the synthesis of the biaxially-textured
buffer layer suitable for HTS films capable of carrying high critical current densities has
employed the ion-assist process to produce both the in-plane and out-of-plane texture. In
order to realize an HTS film possessing a high critical current on a biaxially textured
substrate, the buffer layer architecture should satisfy rigorous requirements. The grains within
the topmost buffer layer construct desirably provide a common in-plane and out-of-plane
crystallographic texture with a mosaic spread of generally less than 20 degrees, with lower
mosaic spreads such as less than 10 degrees presiding better superconducting articles.

[0004] The top layer should generally be chemically compatible with the
superconductor so as to not react during superconductor deposition and be mechanically
robust to prevent microcrack formation at the HTS/buffer layer interface. To date, biaxially
textured buffer layers that have met these objectives generally rely on the use of the ion-assist
(EBAD) process in determining the in-plane and out-of-plane texture. For example, biaxially
textured yttria-stabilized zirconia (YSZ) buffer layer can be formed by IB AD with the (100)
in-plane and (001) out-of-plane texture by directing an Art- beam flux oriented 55 degrees
from the surface normal, which corresponds to the [111] direction for a (001)-oriented cubic
material.
[0005] While the above-described IBAD process has provided the desired biaxial
texture requiring a relatively high thickness (> 1 µm), such as by use of a YSZ film deposited
in the presence of the Ar+ beam, the process is relatively slow and as a result expensive. The
speed and price of such process is a significant issue in the large-scale production of
superconducting tapes, since it would affect the ability to produce a low-cost HTS tape. A
second approach involves the [BAD deposition of MgO requiring a sub-10 nm control of the
nudeation process, typically employing an in-situ monitoring technique, such as reflection
high energy electron diffraction, for controlling the crystallographic texture. This approach is
difficult to employ for large-scale production. Also, the quality of MgO films deposited by
BAD has been found to be extremely sensitive to minor variations in the processes and
structures used for this material.
[0006] Accordingly, there is a need in the art for improved superconductor
components, including coated HTS conductors, processes for forming same, and articles
incorporating same. In particular, there is a need for commercially viable HTS conductors
having characteristics enhancing large-scale production, and processes for forming the same. .


[0007] Accordingly, there is also a need in the art for an alternative technique that
would require less thickness than that required for EBAD of YSZ, but would be more robust
and less sensitive than the IB AD process for MgO.


SUMMARY OF THE INVENTION
[0008] A superconductor article includes a substrate and a first buffer film disposed
on the substrate. The first buffer film has a uniaxial crystal texture characterized by (i)
texture in a first crystallographic direction that extends out-of-plane of the first buffer film
with no significant texture in a second direction that extends in-plane of the first buffer film,
or (ii) texture in a first crystallographic direction that extends in-plane of the first buffer film
with no significant texture in a second direction that extends out-of-plane of the first buffer
film. A second buffer film is disposed on the first buffer film, the second buffer film having a
biaxial crystal texture. A superconductor layer can be disposed on the second buffer film. As
used herein, the term "disposed on" is used to refer to the relative location of the elements in
an article, and does not necessarily require direct contact between the described elements or
components (unless otherwise described as such), and may include intervening layers or
films. Accordingly, the term is used in a general sense regarding orientation or location, as
generally illustrated in the drawings For example, a protective layer can be disposed
between the substrate and the first buffer film.
[0009] The uniaxially textured crystallographic direction of the first buffer film can
be in-plane or out-of-plane. In the case of out-of-plane texture, the out-of-plane crystal
texture can be generally aligned along the [001] crystal direction. The out-of-plane texture
can have a mosaic spread no more than about 30 degrees, preferably no more than about 20
degrees, or more preferably no more than about 10 degrees.
[0010] The first buffer film can have a rock-salt-like crystal structure or may exhibit
anisotropic growth habits. The first buffer film can include REBa2Cu3O7, Bi4Ti3O12, MgO or
NiO. The substrate can be a metal alloy, such as a Ni-based alloy.
[0011] The biaxially textured second buffer film can be aligned along a first axis _
along the [001] crystal direction, and along a second axis having a crystal direction selected


from the group consisting of [111], [101], [113], [100], and [010], The second buffer film can
have a rock-salt-like crystal structure. In this embodiment, the second buffer film can be
MgO, NiO, YSZ, CeO2, Y2O3, TiO2, SnO2, Mn3O4, Fe3O4, Cu2O or RE2O3, where RE is a
rare earth element.
[0012] The superconductor article can provide a Jc of at least 0.S MA/cm2 at 77 K
and self-field, and preferably at least 1.0 MA/cm2 at 77 K and self-field. The superconductor
layer can comprise REBa2Cu3O7-, where RE is a rare earth element. RE can comprise Y. The
superconductor article can comprise a superconductor tape.
[0013] A power cable includes a plurality of superconductive tapes, each tape
comprising a substrate, a first buffer film disposed on the substrate, the first buffer film
having uniaxial crystal texture characterized by (i) texture in a first crystaliographic direction
that extends out-of-plane of the first buffer film with no significant texture in a second
direction that extends in-plane of the first buffer film, or (ii) texture in a first crystaliographic
direction that extends in-plane of the first buffer film with no significant texture in a second
direction that extends out-of-plane of the first buffer film. A second buffer film is disposed on
the first buffer film, the second buffer film having a biaxial crystal texture. A superconductor
layer is disposed on the second buffer film. A conduit can be provided for passage of coolant
fluid through the cable. The superconductive tapes can be wrapped around the conduit. 'The
power cable can comprise a power transmission cable or a power distribution cable.
[0014] A power transformer includes a primary winding, and a secondary winding,
wherein at least one of the primary winding and secondary winding comprises a wound coil
of superconductive tape as described above. The secondary winding can have fewer or more
windings as compared to the primary winding.
[0015] A power generator includes a shaft coupled to a rotor comprising
electromagnets comprising rotor coils, and a stator comprising a conductive winding


surrounding the rotor, wherein at least one of the winding and the rotor coils comprise a
superconductive tape as described above. At least one of the rotor coils can include the
superconductive tape.
[0016] A power grid comprising a power generation station includes a power
generator, a transmission substation comprising a plurality of power transformers for
receiving power from the power generation station and stepping-up voltage for transmission,
a plurality of power transmission cables for transmitting power from the transmission
substation, and a power substation for receiving power from the power transmission cables.
The power substation comprises a plurality of power transformers for stepping-down voltage
for distribution. A plurality of power distribution cables are provided for distributing power
to end users, wherein at least one of the power distribution cables, power transmission cables,
transformers of the power substation, transformers of the transmission substation, and the
power generator includes a plurality of superconductive tapes as described above.
[0017] An electronically active article comprises a substrate, a first buffer film
disposed on the substrate, the first buffer film having uniaxial crystal texture characterized by
(i) texture in a first crystallographic direction that extends out-of-plane of the first buffer film
with no significant texture in a second direction that extends in-plane of the first buffer film,
or (ii) texture in a first crystallographic direction that extends in-plane of the first buffer film
with no significant texture in a second direction that extends out-of-plane of the first buffer
film. A second buffer film is disposed on the first buffer film, the second buffer film having a
biaxial crystal texture. An electronically active layer is disposed on the second buffer film.
The electronically active layer can be a semiconductor, a photovoltaic, a ferroelectric or an
optoelectric layer.
[0018] A method for producing a biaxially textured article comprises the steps of
providing a substrate, forming a first buffer film on the substrate, the first buffer film having
6

uniaxial crystal texture characterized by (i) texture in a first crystallographic direction that
extends out-of-plane of the first buffer film with no significant texture in a second direction
that extends in-plane of the first buffer film, or (ii) texture in a first crystallographic direction
that extends in-plane of the first buffer film with no significant texture in a second direction
that extends out-of-plane of the first buffer film and depositing a second buffer film with ion
assist on the first buffer film, wherein the resulting second buffer film has biaxial texture. The
method can include the step of depositing a superconductor layer on the second buffer film.
Ion-beam assisted deposition (IBAD) can be used to deposit the second buffer film.


BRIEF DESCRIPTION OF THE DRAWINGS
[0019] These and other features, aspects, and advantages of the present invention will
become better understood when the following detailed description is read with reference to
the accompanying drawings in which like characters represent like parts throughout the
drawings, wherein:
[0020] PIG-1 illustrates a superconducting tape article, according to an embodiment
of the invention;
[0021] FIG. 2 illustrates a power cable, according to an embodiment of the invention;
[0022] FIG. 3 illustrates details of a single exemplary superconducting cable,
according to another embodiment of the invention;
[0023] FIG. 4 illustrates a power transformer, according to yet another embodiment
of the invention;
[0024] FIG. 5 illustrates a power generator, according to an embodiment of the
invention; and
[0025] FIG. 6 illustrates a power grid, according to another embodiment of the
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Embodiments of the present invention provide a novel HTS article, methods
for forming same, and devices and systems incorporating the same. According to one
feature, a method is provided for forming a biaxially textured buffer layer article using a two-
step process and associated articles, devices and systems. The first step provides a first buffer
film having uniaxial texture, typically characterized by (i) texture in a first crystallographic
direction that extends out-of-plane of the first buffer film with no significant texture in a
second direction that extends in-plane of the first buffer film, or (ii) texture in a first
crystallographic direction that extends in-plane of the first buffer film with no significant
texture in a second direction that extends out-of-plane of the first buffer film. The single
crystallographic direction can be one of an in-plane direction or an out-of-plane direction,
wherein the other crystallographic directions has no significant crystallographic texture.
Thus, the unixially textured first buffer film does not provide biaxial texture.
[0027] According to one embodiment the uniaxial crystal texture extends out-of-
plane, with no significant texturing in-plane. Typically, it is considered that 'in-plane' is
defined by tvvo mutally perpendicular directions in the plane of the buffer film. According to
another embodiment, the uniaxial crystal texture extends in one of the in-plane directions,
with no significant texturing out-of-plane, and no texturing in the mutually perpendicular in-
plane direction. As used herein, the term "texture", whether referring to in-plane or out-of-
plane texture, refers to a grain-to-grain crystallographic misorientation "mosaic spread" of the
respective layer. Typically, the mosaic spread for a textured layer is less than about 30
degrees, such as less than about 20 degrees, 15 degrees, 10 degrees, or 5 degrees, but is
generally finite typically being greater than about 1°. According to one embodiment, the
term "no significant texture," generally refers to a grain-to-grain misorientation "mosaic


spread" of the respective layer being greater than about 30 degrees and including generally
random polycrystalline arrangements.
[0028] Regarding the out-of-plane crystallographic texture, the mosaic spread is
generally represented by a full-width-at-half-maximum value of an x-ray diffraction peak,
such as obtained by a (001) pole figure measurement. In this case, the (001) crystallographic
planes of the grains are aligned and thus textured in a direction perpendicular to the normal to
the film within an angular spread of less than about 30 degrees.
[0029] A second buffer film is disposed on the first buffer film, the second buffer film
having a biaxial crystal texture. A biaxially textured second buffer film by definition has both
in-plane and out-of-plane crystal texture. A biaxially textured layer is defined herein as a
polycrystalline material in which both the crystallographic in-plane and out-of-plane grain-to-
grain misorientation of the topmost layer is less than about 30 degrees, such as less than
about 20 degrees, 15 degrees, 10 degrees, or 5 degrees, but is generally finite typically
greater than about 1 °. The degree of biaxial texture can be described by specifying the
distribution of grain in-plane and out-of-plane orientations as determined by x-ray diffraction.
A full-width-half-maximum (FWHM) of the rocking curve of the out-of-plane (A8) and in-
plane (∆Φ) reflection can be determined. Therefore, the degree of biaxial texture can be
defined by specifying the range of ∆θ and ∆Φ for a given sample.
[0030] The first buffer film is generally formed without the use of an ion beam while
the second step which forms the second buffer layer film uses an ion-beam assisted
deposition (IBAD) process to produce a biaxially textured layer portion on top of the first
buffer layer portion. The ability to obtain a biaxially textured buffer surface using DBAD
without the associated manufacturing issues relating to use of IBAD for the entire buffer
layer can produce high performance articles substantially more efficiently and economically
as compared to conventional IB AD processing. Embodiments of the present invention thus


conditions, since lower process tolerances can be accepted, which is preferable in a
manufacturing environment. This is believed to be due to the concept that it is energetically
favorable, from a crystal nucleation and growth viewpoint, for the deposited material to align
along the uniaxial crystallographic direction during deposition, creating more flexibility in
BAD film processing.
[0031] A biaxially textured electronically active layer can be disposed on the
biaxially textured buffer layers formed according to embodiments of the invention. The
electronically active layer may be a superconductor, a semiconductor, a nhotovoltaic, a
ferroelectric or an optoelectric. or any other electromagnetic device wherein grain boundary
control is important. In this regard, aspects of the present invention are particularly suitable
for providing high temperature supercondutor components, in which the electronically active
layer is formed principally of a superconducting material. Aspects of the invention are
particularly well suited for the formation of electronically active wire and tape (hereafter a
"tape") articles which have biaxial texture. As used herein, the term "tape" refers to an article
having an aspect ratio uot less than about 1,000, the aspect ratio meaning the ratio of longest
dimension (length) to next longest dimension (width). Typically, the aspect ratio is greater
than about 104, and even greater than about 105.
[0032] The biaxially textured buffer layers are suitable for the formation of a high
temperature superconducting article which provides a critical current density in excess of
about 0.5 MA/cm2 at about 77 K and self-field, and preferably in excess of about 1 MA/cm2.
Embodiments of the invention is also useful for a variety of other electronic applications in
which sharp crystallographic texture is important.
hi the description and appended claims, the conventional index system for denoting
crystal direction through vectors, has been used, which are similar to the Miller
Indices, used for defining crystal planes.


[0033] FIG. 1 shows a tape article 10 according to an embodiment of the invention
having a multi-layer composition including a textured superconductor tape 18 having biaxial
texture along its entire length. The tape article 10 is expected to be particularly useful for
increasing the current carrying capability and reducing AC resistive losses of power
transmission lines. Superconductor article 10 consists of a substrate 12. The substrate 12 can
be a metal or polycrystalline ceramic. In case of a metal, the substrate 12 can be an alloy,
such as a Ni-based alloy. Texture in the substrate 12 is generally not required. Thus, substrate
12 can be polycrystalline or amorphous. Polycrystalline substrates may be utilized for some
applications requiring certain thermal, mechanical, and electrical properties offered by such
materials, such as commercially available Ni-based alloys, such as the Hasteiioy ® group of
high performance substrate materials. The substrate 12 provides support for the
superconductor article 10, and can be fabricated over long lengths and large areas using the
aspects of the present invention. When the superconductor tape is of long length (e.g. 1 km).
First buffer layer 14 and second buffer layer 16 may be deposited on biaxially-textured
substrate surface 12 using a suitable translation process, such as reel-to-reel translation.
[00341 Optional protective layer 13 is generally polycrystalline and is disposed on the
top surface of substrate 12. Protective layer 13 is preferably used when buffer layer 14 is
chemically incompatible with substrate 12. The polycrystalline protective layer is preferably
an oxide, such as cerium oxide or yttria-stabilized zirconia (YSZ).
[0035] A second buffer layer 16 is disposed on the first buffer layer 14. First buffer
layer 14 provides texture in a first crystallographic direction that extends out-of-plane of the
first buffer film with no significant texture in a second direction that extends in-plane of the
first buffer film, or (ii) texture in a first crystallographic direction that extends in-plane of the
first buffer film with no significant texture in a second direction that extends out-of-plane-of
12

the first buffer film, while second buffer layer 16 provides biaxial texture. Epitaxially-grown
superconducting layer 18 is disposed on biaxially texture buffer layer 16.
[0036] Although not shown in FIG. 1, at least one epitaxial film can be provided
between the second buffer layer 16 and the superconductor layer 18. In addition, a noble
metal layer can overlay the superconductor layer 18, such as Ag.
[0037] This high degree of out-of-plane texture in first buffer layer 14 can be
achieved either through the anisotropic growth habits of selected materials or by preferential
selection of energetically favorable growth orientations of selected materials. In this
application, the film that produces the uniaxial texture, such as out-of plane texture, is
provided without the need for ion assist and is referred to as Layer t. For example, Layer 1
can be a polycrystalline material where the energetically favorable growth direction is
along the film normal. Examples are rock-salt structures such as MgO and NiO, which have a
tendency to align preferentially in the energetically favorable direction of irrespective
of the underlying substrate orientation. U.S. Pat. No. 6,190,752 to Do ct al. entitled "Thin
films having rock-salt-like structure deposited on amorphous surfaces" provides detailed
information regarding rock-salt structures and available species.
[0038] Several polycrystalline thin-film materials, including various oxides, have
anisotropic growth habits as they tend to align a specific crystallographic axis along the
surface normal of a substrate for certain deposition conditions. In terms of anisotropic
growth, several multi-cation oxides can be used. For example, the use of REBa2Cu3O7,
where RE is a rare earth element such as YBa2Cu3O7, and Bi4Ti3O12. and wherein both exhibit
out of plane (c-axis) oriented film growth on randomly oriented substrates. Uniaxially
textured films can be used as buffer layer 14 which can act as an initial template for epitaxial
growth (including IB AD films) to form biaxially textured buffer layer 16. Buffer layer 14.
generally has a thickness within a range about 100 to about 3000 Angstroms. Buffer layer 14


is preferably aligned along the [100] direction and can be deposited by sputtering, pulsed
laser deposition, or evaporation.
[0039] Second buffer layer 16 is a layer in which in-plane texture is generally induced
due to the ion beam and is also referred to herein as Layer 2. Without any ion beam present
during epitaxy, the epitaxial growth of buffer layer 16 on the uniaxial out-of-plane textured
buffer layer 14 will reproduce the uniaxial texture achieved in buffer layer 14. By imposing
an ion beam (e.g. Ar) along a high-symmetry direction of buffer layer 16 during epitaxy of
buffer layer 16, the growth of grains oriented with a preferred axis aligned along the ion
beam direction are generally preferred over those grains with other orientations. This
subsequent IBAD growth induces an in-plane texture component in buffer layer 16 that does
not exist in buffer layer 14, while still maintaining the out-of-plane texture.
[0040| The second buffer layer 16 generally has a thickness within a range of about
100 to about 5000 Angstroms. The superconductor layer 18 thickness is generally from about
500 to about 10,000 run. The biaxially textured second buffer layer 16 is preferably aligned
along a first axis having along a [001] crystal direction, and along a second axis having a
crystal direction selected from the group consisting of [111], [101], [113], [100], and [010].
The second buffer layer 16 can have a rock-salt-like crystal structure and comprise MgO,
NiO or be selected from YSZ, CeO2, Y2O3, TiO2, SnO2, Mn3O4, Fe3O4, Cu2O, or RE2O3,
wherein RE is a rare earth element. Buffer layer 16 can be deposited by sputtering or
evaporation.
[0041] Superconductor layer 18 is preferably an oxide superconductor. The oxide
superconductor is preferably selected from REBa2Cu3O7 where RE is a rare earth element,
such as Y, and related compounds. The superconductor anicle 10 can provide a Jc of at least
about 0.5 MA/cm2 at about 77 K and self-field and preferably at least about 1 MA/cm2. -


[0042] Although aspects of the invention are generally described using a c-axis
textured first buffer layer 14. the invention is in no way limited to this embodiment. In
another embodiment of the invention, the uniaxial crystal structure in the first buffer film 14
could also be along one direction within the plane of the film (a-axis or b-axis). In this
embodiment, there is no preferential texture in a plane perpendicular to the axis along which
the crystals are textured within the film plane (c-axis). One example of this embodiment is
that of fiber texture, where a preferential uniaxial texture is present along the long direction
of a tape or a wire but no preferential texture is present in the plane perpendicular to this
direction.
[0043] A general embodiment of the invention involves providing a substrate for film
growth. The substrate is cleaned with solvents, such as acetone, methanol, and
trichloroethylcne. The substrate is mounted in a deposition chamber suitable for thin film
deposition. A polycTystalline protective layer is then optionally deposited on the substrate.
The polycrystalline layer prevents a chemical reaction from occurring between Layer I and
the substrate.
[0044] The protective layer coated substrate is heated in an ambient suitable for the
deposition of an anisotropic thin film or a thin film whose energetically favorable growth
direction is (layer 1). Layer 1 is then deposited and provides out-of-plane (c-axis)
texture without the need for ion assist. The Layer 1 coated substrate is then transferred to a
thin-film deposition system equipped with an ion gun. The substrate is heated to a
temperature suitable for the epitaxial growth of Layer 2 on Layer 1. Vacuum deposition is
employed to deposited Layer 2 on Layer 1 in the presence of the ion beam, which is directed
along a preferred crystallographic direction of the material constituting Layer 2 to induce in-
plane texture during epitaxy.
15

[0045] The invention is useful for a wide variety of applications, particularly
superconductor applications. Regarding superconductor applications, the invention can be
used to form high temperature superconducting wires or tapes which can be used for
transmission lines, motors, generators, or high-field magnet applications.
[0046] FIG. 2 illustrates a power cable 200, according to an embodiment of the
invention. Power cable 200 shown includes three superconducting cables 220 arranged in a
trefoil arrangement where all three phases are housed in the same thermally insulating
conduit 230. Ground plane 240 is also shown. The phases are situated as close together as
physically possible. Although not shown, other arrangements are possible, including a
concentric arrangement where the 3 cables are situated concentrically.
[0047] Figure 3 shows details of a single exemplary superconducting cable 220.
Proceeding from the outside to the inside of cable 220, cable 220 includes enclosure 366, skid
wires 364, corrugated steel 362 and thermal insulator 360. LN2 duct 358 provides refrigerant
to cable 220 and is disposed on centering wires 356. Copper shield 354 is provided and is
disposed on superconductor tape layer 352. Dielectric tape 350 is disposed between tape layer
352 and copper shield 348. Another superconductor tape layer 346 is beneath copper shield
348. Former/duct 344 provides a passage of coolant fluid, such as liquid nitrogen (LN2)
refrigerant which permits inexpensive cooling to temperatures above the freezing point for
nitrogen (which is at about 63.3 K). The power cable 200 can be used as a power
uansmission cable or a power distribution cable.
[0048] FIG. 4 illustrates power transformer 400. according to another embodiment of
the invention. Power transformer 400 includes a primary winding 472, a secondary winding
474 and core 476. At least one of the primary winding 472 and secondary winding 474
comprises a wound coil of superconductive tape as described above embedded in an insulaing..


material such as epoxy. The secondary winding 474 can have fewer or more windings as
compared to the primary winding 472.
[0049] FIG. 5 illustrates power generator 500, according to an embodiment of the
invention. Power generator 500 includes a turbine 582 and a shaft 584 coupled to a rotor 586
comprising electromagnets comprising rotor coils, and a stator 588 comprising a conductive
winding surrounding the rotor, wherein at least one of the winding and the rotor coils
comprises a superconductive tape as described above.
[0050] FIG. 6 illustrates a power grid 600, according to another embodiment of the
invention. Power grid 600 includes a power generation station comprising a power generator
plant 690 and transmission lines 692 to deliver power to transmission substation 694.
Transmission substation 694 includes transformers 695. Power transmission cables 696
emanate from transmission substation 694. Power transmission cables 696 deliver power
from transmission substation 694 to power substation 698 which mcludes a plurality of power
transformers 697 for stepping-down voltage for distribution. Power distribution cables 610
deliver power from power substation 698 to end users 602. At least one of the power
distribution cables 610, power transmission cables 696, transformers 697 of the power
substation 698, transformers of the transmission substation 695, and the power generator
plant 690 comprise a plurality of superconductive tapes as described above.
Examples
[0051] It should be understood that the examples and embodiments described herein
are for illustrative purposes only and that various modifications or changes in light thereof
will be suggested to persons skilled in the art and are to be included within the spirit and
purview of this application. The invention caniake other specific forms without departing
from the spirit or essential attributes thereof.


Example 1
[0052] A Ni-based alloy substrate is provided for film growth. The substrate is
cleaned with solvents, such as acetone, methanol, and trichloroethylene. The substrate is
mounted in a pulsed-laser deposition chamber for thin film deposition. A polycrystalline
yttria-stabilized zirconia (YSZ) protective layer is deposited on the substrate using pulsed
laser deposition at about 25°C under vacuum. This protective layer prevents chemical
reactions between layer 1 and the substrate.
[0053] The coated substrate is heated to about 700°C in vacuum for the deposition of
an YBa2Cu3O7 thin film (Layer 1). A YBa2Cu3O7 film of thickness about 300 nm is deposited
at about 700°C in about 200 mTorr of oxygen. The film is c-axis oriented, but randomly
oriented in-plane. The substrate is then transferred to a thin-film deposition system equipped
with an ion gun. The substrate is heated to a temperature suitable for the epitaxial growth of
MgO on YBa2Cu3O7 on Layer 1. Pulsed laser deposition is employed to deposit epitaxial
MgO on the YBa2Cu3O7 template. The MgO layer will be (001) textured. This is followed by
the growth of CeO2 in the presence of an Ar ion beam, which is directed along either the
[111] or [110] crystallographic direction of CeO2.
Example 2
[0054] A Ni-based alloy substrate is provided for film growth. The substrate is
cleaned with solvents, such as acetone, methanol, and trichloroethylene. The substrate is
mounted in a pulsed-laser deposition chamber for thin film deposition. A MgO film of
thickness of about 100 nm (Layer 1) is deposited at about 25°C in vacuum. The MgO layer
will be (001) textured. The coated substrate is then transferred to a thin-film deposition


system equipped with an ion gun. A second layer of MgO (Layer 2) is grown in the presence
of an Ar ion beam, the ion beam being directed along either the [111] or [110]
crystallographic direction of MgO. The second MgO layer (Layer 2) will be biaxially
textured.
It should be understood that the examples and embodiments described herein
are for illustrative purposes only and that various modifications or changes in light thereof
may be made by persons skilled in the art without departing from the scope of the present
claims.
The invention disclosed and claimed in the instant patent application is not useful for
or relate to the production, control, use or disposal of atomic energy or the prospecting,
rnining, extraction, production, physical and chemical treatment, fabrication, enrichment,
canning or use or any 'prescribed substance' or radioactive substance or the ensuring of safety
in atomic energy operations. Further, the invention is also not relevant for defense purpose.
The applicant disclaims any use of the invention for atomic energy purpose or for defense
purpose.


We claim:
1. An electronically active article (10), comprising:
a substrate (12);
a first buffer film (14) disposed on said substrate, said first buffer film having uniaxial
crystal texture characterized by (i) texture in a first crystallographic direction that extends
out-of-plane of the first buffer film with no significant texture in a second direction that
extends in-plane of the first buffer film, or (ii) texture in a first crystallographic direction that
extends in-plane of the first buffer film with no significant texture in a second direction that
extends out-of-plane of the first buffer film;
a second buffer film (16) disposed on said first buffer film, said second buffer film
having a biaxial crystal texture; and
an electronically active layer (18) disposed on said second buffer film, wherein said
electronically active layer (18) provides a Jc of at least 0.5 M A/cm2 at 77 K and self-field, if
the electronically active layer (18) is a superconductor.
2. The article as claimed in claim 1, wherein said electronically active layer is
selected from the group consisting of a superconductor, a semiconductor, a photovoltaic, a
ferroelectric or an optoelectric.
3. A article as claimed in claim 1, wherein said electronically active layer
comprises a superconductor layer
4. The article as claimed in claim 1, wherein said first buffer film (14) has out-of-
plane of crystallographic texture.
20

5. The article as claimed in claim 4, wherein said out-of-plane crystal texture is
generally aligned along the [001] crystal direction.
6. The article as claimed in claim 4, wherein said out-of-plane texture has a mosaic
spread between 1 to 30 degrees.
7. The article as claimed in claim 4, wherein said out-of-plane texture has a mosaic
spread between 1 to 20 degrees.
8. The article as claimed in claim 4, wherein said out-of-plane texture has a mosaic
spread between 1 to 10 degrees.
9. The article as claimed in claim 1, wherein said first buffer film (14) has a rock-
salt-like crystal structure.
10. The article as claimed in claim 1, characterized in that the first buffer film (14)
comprises at least one selected from the group consisting of REBa2Cu3O7, Bi4Ti3O12, MgO,
and NiO.
11 The article as claimed in claim 1, wherein said substrate (12) comprises a metal
alloy.
12. The article as claimed in claim 11, wherein said metal alloy comprises a Ni-based
alloy.
13. The article as claimed in claim 1, wherein said biaxially textured second buffer
film (16) is aligned along a first axis along a [001] crystal direction, and along a second axis


having a crystal direction selected from the group consisting of [111], [101], [113], [100], and
[010].
14. The article as claimed in claim 1, wherein said second buffer film has a rock-salt-
like crystal structure.
15. The article as claimed in claim 14, wherein said second buffer film (16)
comprises at least one material from the group consisting of MgO, NiO, YSZ, CeO2, Y2O3,
TiO2, SnO2, Mn3O4, Fe3O4, Cu2O, and RE2O3, wherein RE is a rare earth element.
16. The article as claimed in claim 1, wherein said superconductor layer comprises
REBa2Cu3O7, wherein RE is a rare earth element.
17. The article as claimed in claim 15, wherein RE comprises Y.
18. The article as claimed in claim 1, wherein said article is in the form of a
superconductor tape.
19. The article as claimed in claim 1, further wherein a protective layer disposed
between said substrate and said first buffer film.
20. A power cable incorporating superconductor tape as claimed in claim 18,
21. A method of producing the article as claimed in any one of claims 1-19,
comprising the steps of:
(a) providing a substrate (12);


(b) forming a first buffer film (14) on said substrate, said first buffer film having
uniaxial crystal texture characterized by (i) texture in a first crystallographic direction that
extends out-of-plane of the first buffer film with no significant texture in a second direction
that extends in-plane of the first buffer film, or (ii) texture in a first crystallographic direction
that extends in-plane of the first buffer film with no significant texture in a second direction
that extends out-of-plane of the first buffer film;
(c) depositing a second buffer film (16) with ion assist on said first buffer film,
said second buffer film having a biaxial texture; and
(d) depositing an electronically active layer such as a superconductor layer on said
second buffer film, wherein said superconducting layer (18) provides a Jc of at least 0.5 MA/
cm2 at 77 K and self-field.

22. The method as claimed in claim 21, wherein said article is in the form of a
superconductor tape.
23. The method as claimed in claim 21, wherein a process comprising ion-beam
assisted deposition (IBAD) is used to deposit said second buffer film.
24. The article as claimed in claim 1, comprising:
a substrate (12);
a first buffer film (14) disposed on said substrate, said first buffer film comprising a
polycrystalline oxide thin film material;
a second buffer film (16) disposed on said first buffer film, said second buffer film
comprising a material from the group consisting of IBAD MgO, IBAD CeO2, or IBAD
RE2O3, where RE is a rare earth element, and having a biaxial crystal texture; and
a superconductor layer (18) disposed on said second buffer film.


25. The article as claimed in claim 24, wherein said second buffer film comprises
IBAD MgO.
26. The article as claimed in claim 1, comprising:
a substrate (12) ;
a first buffer film (14) disposed on said substrate, said first buffer film comprising a
polycrystalline material having the rock salt-like crystal structure;
a second buffer film (16) disposed on said first buffer film, said second buffer film
comprising a material from the group consisting of IBAD MgO, IBAD CeO2, or IBAD
RE2O3, where RE is a rare earth element, and having a biaxial crystal texture; and
a superconductor layer (18) disposed on said second buffer film.
27. The article as claimed in claim 26, wherein said polycrystalline material has
the rock salt crystal structure.
28. The article as claimed in claim 26, wherein the second buffer film comprises
IBAD MgO.

Documents:


Patent Number 247522
Indian Patent Application Number 2552/KOLNP/2005
PG Journal Number 16/2011
Publication Date 22-Apr-2011
Grant Date 13-Apr-2011
Date of Filing 09-Dec-2005
Name of Patentee UNIVERSITY OF FLORIDA RESEARCH FOUNDATION, INC.
Applicant Address 223 GRINTER HALL, P.O. BOX 115500, GAINESVILLE, FL
Inventors:
# Inventor's Name Inventor's Address
1 SELVAMANICKAM VENKAT 29 FRANCIS DRIVE, WYNANTSKILL, NY 12198
2 NORTON DAVID P 2449 NW 93RD STREET, GAINESVILLE, FL 32606
PCT International Classification Number H01L 39/24
PCT International Application Number PCT/US2004/018319
PCT International Filing date 2004-06-09
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/457,184 2003-06-09 U.S.A.